Radiation survival curve parameters for human lymphocytes

This paper estimates radiation survival curve parameters for lymphocytes in order to optimize large-field radiation schedules for patients with lymphoma or patients requiring immunosuppression. The authors compared radiation schedules (total body or total lymphoid) used in 12 different studies in dogs, pigs, rhesus monkeys, or human patients. Different radiation schedules should cause the same survival fraction for lymphocytes if results are similar and cause at least a threefold difference in survival fractions if results are dissimilar. By trial and error, the best extrapolation number (n) and D0 can be selected for each data set by using the single-hit, multiple-target model. Data sets are best explained by postulating an n of 1.25-1.50 and a D0 of 1.5 Gy for malignant (B lymphocytes) or normal lymphocytes. Both are higher than previous estimates made by other investigators determining lymphocyte numbers in peripheral blood after radiation exposure or by using radiation conditions unrealistic for human patients that can be achieved only in small rodents